What is the maximum equivalent length of a boiler’s flue?
October 24th 2023
The maximum horizontal equivalent flue lengths (after the first elbow) is: 20m
The maximum vertical equivalent flue lengths is: 21m
Allow 1.3 meters of flue length for each 87° bend
1.0 meters of flue length for each 45° bend.
| Maximum horizontal equivalent flue lengths (m) | Maximum vertical equivalent flue lengths (m) | 87° Elbow (m) | 45° Elbow (m) | |
| NCB-CE | 20 | 21 | 1.3 | 1.0 |
| NCB300 | 7 | 8 | 1.3 | 1.0 |
| NCB500 | 7 | 8 | 1.3 | 1.0 |
| NCB700 | 20 | 21 | 1.3 | 1.0 |
| LCB700 | 20 | 21 | 1.3 | 1.0 |
| NPE A/S | 20 | 21 | 2.4 | 1.2 |
Note: The maximum horizontal equivalent flue length is measured after the first elbow.
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